1. Technical Field
The present disclosure relates to a carbon nanotube based thermionic emission device.
2. Description of Related Art
Thermionic emission devices are widely applied in gas lasers, arc-welders, plasma-cutters, electron microscopes, x-ray generators, and the like. Thermionic emission devices are constructed by forming an electron emissive layer made of alkaline earth metal oxide on a base. The alkaline earth metal oxide includes BaO, SrO, CaO, or a mixture thereof. The base is made of an alloy including at least one of Ni, Mg, W, Al, and the like. When thermionic electron emission devices are heated to a temperature of about 800° C., electrons are emitted from the thermionic emission source. Since the electron emissive layer is formed on the surface of the base, an interface layer is formed between the base and the electron emissive layer, the electron emissive alkaline earth metal oxide easily splits off from the base. Further, thermionic electron emission devices are less stable because alkaline earth metal oxide tends to vaporize at high temperatures. Consequently, the lifespan of the thermionic emission device are low. Further, the response speed of the thermionic emission device to the heating is relatively low. It is difficult to rapidly emit electrons by using a current to heat the thermionic emission device, and rapidly stop the emission by cutting off the current. Thus, it is difficult to achieve a thermionic emission pulse current.
What is needed, therefore, is a thermionic emission device, which has stable and high electron emission efficiency, great mechanical durability, and is able to emit a thermionic emission pulse current.